Powder level sensing

ABSTRACT

Apparatus for sensing and externally signalling the diminution of a supply of developer powder in a tray in which a blunt edged conductive bar is supported by resilient members from a rotating shaft to drag the powder toward a discharge opening and which completes an electrical circuit by touching contacts in the bottom wall of the tray upon diminution of the supply of developer powder to close a circuit and externally signal the diminution of the powder.

United States Patent I Richard C. Berg Bloomington, Minn.

[72] Inventor 21 App], No. 867,495 22 Filed 0ct.20, 1969 [45] Patented July 20, 1971 [73] Assignec Minnesota Mining and Manufacturing Company St. Paul, Minn.

[54] POWDER LEVEL SENSING 7 Claims, 3 Drawing Figs.

v 200/6l.2l, 118/637 51 lnt.Cl ..G08b2l/00 so FieldolSeareh 340/246,

259; ZOO/61261.21; ll8/637; 355/3 [56] References Cited UNITED STATES PATENTS 2,909,766 10/1959 Bozich ZOO/61.21 2,977,772 4/1961 Dawson 340/246 Primary Examiner.lohn W. Caldwell Assistant Examiner-Howard S. Cohen Attorney-Kinney, Alexander, Sell, Steldt & Delah unt ABSTRACT: Apparatus for sensing and externally signalling the diminution of a supply of developer powder in a tray in which a blunt edged conductive bar is supported by resilient members from a rotating shaft to drag the powder toward a discharge opening and which completes an electrical circuit by touching contacts in the bottom wall of the tray upon diminution of the supply of developer powder to close a cir-' cuit and externally signal the diminution of the powder.

POWDER LEVEL SENSING This invention'relates to an improved apparatusfor use with a supply tray having. a bottom wall forsensing the diminution of a supply of developer powder in thetray and for externally blocked by developer powder and which shines through a I transparent window when the supply of developerpowder is diminishedtMore recently, however, it has been found-advantageous to remotely indicate thediminution of the supply of developer powder so that the supply may be maintained at any desired location-as, for example, withina photocopying machine. This has beenattempted by-the use of a photocell which is directed towards light and activated upon diminution of the supply of powder. between the two. However, this arrangement has been undesirable since the photocell may become coated with developer powder and it will not be. activated even when the entire supply of powder has been used.

According to the present invention an apparatus is provided which mechanically senses the diminution of a supply of developer powder and remotely indicates the same. The'apparatus also provides for movementof developer powder toward a dispensing. position at the same time;it senses the diminutiottofa supply of powder.

The present invention has the advantages desired of apparatus for use with a hidden supply tray having a bottomwall for sensing the diminution of a-supplyof developer powder in the tray and comprises a shaft rotated above the. bottomwall of the tray, spaced electrical contact means on the bottom wall of the tray, a. conductive bar having a blunt surface to restrict penetration of the bar when contacting the supply of developer powder, resilient means for connecting the bar to the shaft to provide movement of the bar about the axis of the shaft and for permitting the barto float on. a supply ofipowder and to contact the contact-meansupon diminution of-the supply'of powder over the contact means, and signal means responsive to contact of the bar andvthe electrical contact means for indicatingthe diminution of a supply of developer powder by'flashing a light or causing an intermittent audible signal, or other signal to be actuated.

The novel features and advantages of the presentlinvention will become more apparent after reading the following description which refers to the accompanying drawings, wherein:

P16. 1' is a perspective view of apparatus for sensingrthe diminution of a supply of developer powder made in accordance with the present invention;

FIG. 2- is a schematic view illustrating the device of FIG. 1 in use with'developer powder at a first level; and

1 16.3 is a schematic view illustrating the device of FIG. 1 in use with developer diminished to a second level.

Apparatus for sensing the diminution of a supply of developer powder constructed in accordance with the present invention-and generally designated 10, is illustrated in FIG. 1

and comprises a shaft 12, a pair of resilient radial arms, such .as helical springs 14 and 15, connected to the shaft 12, a conductive bar 17 connected to the springs, a pair of electrical contacts 18-and l9, and a remote signal circuit 21.

The shaft 12 is supported at its ends in a pair ofend plates 23 and 24 for rotation above a bottom normally horizontal wall 27 of a developer powder tray 26 and about an axis parallel to the bottom wall 27 of the tray 26. The electrical contacts 18 and 19 are supported on and suitably insulated from the bottom wall 27 of the tray 26. They are generally triangular in cross section and extend in a'direction perpendicular to. the shaft 12 generally equal distances to each side of a vertical line through the axis of the shaft 12. An insulated lead wire 29 is connected to contact 19 and extends out of the tray 26 and a similar lead wire30 is connected to contact 18. The lead wires 29 and 30 are connected to the signal circuit 21 to form an dicularly from the shaft. The conductive bar17 is formed with a straight section equal to the distance between the springs 14 and 15 and. it is bent atright angles to its length at its ends to extend into the coil of the springs where it is securedhThe .springs 14 and 15 are similar and support theconductive bar 17 with its length parallel to the axis of the shaft 12. The springs 14 and 15 support the bar 17 at asufficient distance 7 from the shaft to contact the conductive bar 17 against both electrical contacts 18 and19 when there. is no powder above thecontacts to complete the signal circuit 21 and thereby to light the lamp 32. The springs 14 and 15 are sufficiently flexible and'the edge of the bar contacting the powder isv sufficiently blunt so thatw-hen there is developer powder 34 in the tray 26 above the electrical contacts 18and 19. the springs will bend to permit the bar 17 to float on a supply of powder and to pass between the shaft l2.and the electrical contacts 18 and 19 without touchingv the contacts. The conductive bar 17 as illustrated is circular in cross section to'restrict its penetration into the powder 34 to aid the springs 14 and 15 in floating it on the powder.

Rotation of the shaft 12 is provided by a pulley 36 secured to the shaft at one end extending through the end plate '24 and driven by a belt 37 in a counterclockwisedirection as viewed "in-FIG. 2. The belt 37 extends around a drive roller 38, an

idler 39, and a pulley for a discharge roller.-40 and then back .to the pulley 36. The drive roller is suitably driven such as 12. If the developer powder 34 is magnetically'responsive the discharge roller 40 may comprise a nonconductive sleeve .within which magnets are arranged about andsecured to a central shaft with the shaft and the sleeve being relatively rotatable to move powder out of the tray 26 such as for application to an exposed photoconductive web in a document reproducing machine.

In one specific embodiment for use in sensing the diminution of a supply of developer powder which has a mean'particle size of ten microns and a density of about 1.66 gm/cm. (0.06 lb./cu.in.) the conductive-bar 17 is formedof 0.198 cm. (0.078 inch) diameter stainless steel rod. The vertical spacing between, the shaft 12 and the electrical contacts 18 and '19 is about 1.587 cm. (0.625 inch) while the springs 14 and: 15 are 2.54 cm. (1.0 inch) long and are formed of 0.030 cm. (0.012

.inch) wire in aclose wound open wound close wound configuration. To provide the desiredmovement of the powder 34 progress withthe shaft l2.to the-position illustrated in full in FIG. 2. As the, shaft 12 continues to be rotated the resistance of the developer powder 34 flexes the springs 14 and 15 and the conductive bar 17 floats on the supply of powder between the shaft 12 and the electrical contacts 18 and 19 as illustrated in dotted lines in FIG. 2. As the conductive bar 17.is moved through the supply of powder 34 it moves the powder toward the discharge roller 40 for discharge from the tray.26 by the discharge roller 40. As the supply of powder 34 in the tray 26 is diminished it reaches the stage illustrated in FlG.'3.,At this time the conductive bar 17 contacts the electrical contacts 18 said shaft.

3. Apparatus as recited in claim 2 wherein said conductive bar is cylindrical and said springs normally support said bar On each successive pass the conductive bar 17 will make more extensive contact with the electrical contacts 18 and 19 to 7 keep the signal lamp 32 lit for longer periods of time. The flashing signal lamp 32 will attract the operators attention to the need for replenishing the supply of developer powder 34 in the tray 26.

Having thus described the invention, What I claim is:

1. Apparatus for use with a supply tray having a bottom wall for sensing the diminution of a supply of, developer powder in said tray, said apparatus comprising:

a shaft rotatably mounted above said bottom wall,

means for rotating said shaft,

spaced electrical contact means on said bottom wall of said supply tray,

a conductive bar having a blunt surface-to restrict penetration of said bar when contacting a said supply of signal means responsive to contact of said bar and said electrical contact means for indicating the diminution of a said supply of developer powder. 2. Apparatus as recited in claim 1 wherein said resilient means comprises a plurality of helical springs normally extending from said shaft generally perpendicular to the axis of parallel to the axis of said shaft. 4. Apparatus for use with a supply tray'having a bottom wall v for sensing and signalling the diminution of a supply of developer powder in said tray, said apparatus comprising:

a shaft rotatably mounted above said bottom wall, means for rotating said shaft, r I a bar having a blunt surface to restrict penetration of said bar when contacting a said supply of developer powder while affording movement of saidsupply of powder in the 1 direction of movement of said bar,

resilient means for connecting said bar to said shaft to provide movement of said bar with said shaft about the axis of said shaft, to permit said bar to float on said supply of powder and to increase the displacement of said bar from said shaft upon diminution of said supply of developer powder, and

signal means responsive to increased displacement of said bar from said shaft for indicating the diminution of a said supply of developer powder.

5. Apparatus as recited in claim 4 wherein said resilient means comprises a plurality of helical springs normally extending from said shaft generally perpendicular to the axis of said shaft.

6. Apparatus as recited in claim 5 wherein said bar iscylindrical and said springs normally support said bar parallel to the axis of said shaft.

7. Apparatus as recited in claim 4 wherein said bar is electrically conductive, wherein said signal means includes spaced electrical contact 'means, and wherein said resilient means connects said bar to said shaft to contact said bar against said contact means upon diminution of a said supply of developer powder, 

1. Apparatus for use with a supply tray having a bottom wall for sensing the diminution of a supply of developer powder in said tray, said apparatus comprising: a shaft rotatably mounted above said bottom wall, means for rotating said shaft, spaced electrical contact means on said bottom wall of said supply tray, a conductive bar having a blunt surface to restrict penetration of said bar when contacting a said supply of developer powder while affording movement of said supply of powder in the direction of movement of said bar, resilient means for connecting said bar to said shaft to provide movement of said bar about the axis of said shaft and for permitting said bar to float on a said supply of powder and to contact said contact means upon diminution of a said supply of developer powder above said contact means, and signal means responsive to contact of said bar and said electrical contact means for indicating the diminution of a said supply of developer powder.
 2. Apparatus as recited in claim 1 wherein said resilient means comprises a plurality of helical springs normally extending from said shaft generally perpendicular to the axis of said shaft.
 3. Apparatus as recited in claim 2 wherein said conductive bar is cylindrical and said springs normally support said bar parallel to the axis of said shaft.
 4. Apparatus for use with a supply tray having a bottom wall for sensing and signalling the diminution of a supply of developer powder in said tray, said apparatus comprising: a shaft rotatably mounted above said bottom wall, means for rotating said shaft, a bar having a blunt surface to restrict penetration of said bar when contacting a said supply of developer powder while affording movement of said supply of powder in the direction of movement of said bar, resilient means for connecting said bar to said shaft to provide movement of said bar with said shaft about the axis of said shaft, to permit said bar to float on said supply of powder and to increase the displacement of said bar from said shaft upon diminution of said supply of developer powder, and signal means responsive to increased displacement of said bar from said shaft for indicating the diminution of a said supply of developer powder.
 5. Apparatus as recited in claim 4 wherein said resilient means comprises a plurality of helical springs normally extending from said shaft generally perpendicular to the axis of said shaft.
 6. Apparatus as recited in claim 5 wherein said bar is cylindrical and said springs normally support said bar parallel to the axis of said shaft.
 7. Apparatus as recited in claim 4 wherein said bar is electrically conductive, wherein said signal means includes spaced electrical contact means, and wherein said resilient means connects said bar to said shaft to contact said bar against said contact means upon diminution of a said supply of developer powder. 